Cambrian Stage 2

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Key events in the Cambrian
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Fortunian
"Stage 2"
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Wuliuan
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Guzhangian
Paibian
Jiangshanian
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Baykonurian glaciation
Baykonurian glaciation
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Orsten Fauna
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Burgess Shale
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Kaili biota
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Archaeocyatha extinction
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Emu Bay Shale
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Sirius Passet biota
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Chengjiang biota
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First Trilobites
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SSF diversification, first brachiopods & archaeocyatha
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First halkieriids, mollusсs, hyoliths SSF
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Treptichnus pedum trace
Large negative peak δ 13Ccarb excursion
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First Cloudina & Namacalathus mineral tubular fossils
Stratigraphic scale of the ICS subdivisions and Precambrian/Cambrian boundary.

Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia.[1] Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy.[2] The preferred definitions for the lower boundary are the first appearance of the molluscs Watsonella crosbyi or Aldanella attleborensis around 529 million years ago.[3] The proposed upper boundary might be the first appearance of trilobites around 521 million years ago.[2]

Possible candidates for a GSSP include the first appearance of Watsonella crosbyi in the Zhujiaqing Formation in Yunnan, China or the Pestrotsvet Formation near the Aldan River on the Siberian Platform.[4]

References[edit]

  1. ^ Kouchinsky, Artem; Bengtson, Stefan; Missarzhevsky, Vladimir V.; Pelechaty, Shane; Torssander, Peter; Val'kov, Anatolij K. (24 September 2001). "Carbon isotope stratigraphy and the problem of a pre-Tommotian stage in Siberia". Geological Magazine. 138 (4). doi:10.1017/S0016756801005684.
  2. ^ a b "GSSP List ICS". ICS. Archived from the original on 15 November 2012. Retrieved 9 November 2012.
  3. ^ "International Commission on Stratigraphy".
  4. ^ Li, Guoxiang; Zhao, Xin; Gubanov, Alexander; Zhu, Maoyan; Na, Lin (1 April 2011). "Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2". Acta Geologica Sinica - English Edition. 85 (2): 309–319. doi:10.1111/j.1755-6724.2011.00400.x.
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